Question: Simplify the following expression: $n = \dfrac{1}{2q} - \dfrac{6}{7q}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $2q$ and $7q$ $\lcm(2q, 7q) = 14q$ $ n = \dfrac{7}{7} \cdot \dfrac{1}{2q} - \dfrac{2}{2} \cdot \dfrac{6}{7q} $ $n = \dfrac{7}{14q} - \dfrac{12}{14q}$ $n = \dfrac{7 -12}{14q}$ $n = \dfrac{-5}{14q}$